Montag, 20. Januar 2014

WOGE #422

After searching in vain for #420, I quickly solved WOGE #421 which was a multiple stratovolcano with very nice lava flows. #421 showed some nice features which helped to locate it. This included shadows (southern hemisphere), snow remnants (high altitude) and a volcanic crater, which together guided me to a volcanic more or less active area of the central Andes.

Now it's time to present #422, which covers a completely different topic in the wide range of geology.
It might not be the hardest one, but as there are some interesting things worth to mention about geology, I'll post it anyway. As you can see I considered a tilted picture as best option.

As usual:
Find the location on GoogleEarth and clearly define it's location
(lat/long) for example. You will also have to explain the geology the
best you can. Your prize (and duty) will be to host the next WoGE.

Kommentare:

From the Impact Database: "Notes = Coordinates from Google Earth based on McHone and Greeley (1997) and Sørensen and Bauer (2003), diameter from (Storzer et al., 1971a). Semicircular basin on the west wall of the Otztaler-Ache valley, bound by Maurach barrier in the east thought to be a massive ladslide. A pumice-like material known since 1863; volcanic and impact origin proposed (Storzer et al., 1971a and referrences within). (Kurat and Richter, 1969) described inequilibrium melting in a fussed sample from Koefels and concluded it was formed by an impact. (Storzer et al., 1971a) obtained fission-track age for a fussed rock sample 8.0 ± 6.0 × 10^3 yr consistent with geological and C-14 results. "Lechatelierite, feldspar glasses and probable chaoite in 'Köfelsite' prove that temperatures far above those common for igneous processes existed at the time of formation. The presence of the tomorphic quartz, maskelynite and multiple sets of planar features in quartz and feldspars strongly indicates shock metamorphism" - (Storzer et al., 1971a). (Storzer et al., 1971b) is an abstract and (Storzer et al., 1972) is an erratum of (Storzer et al., 1971a). (Surenian, 1989) reported cleavage in quartz from gneiss and lechtelierite from a pumice-like glass (without providing credible evidence) and concluded that the Koefels slide was triggered by an impact. C. Koeberl reanalyzed the reported plannar features in quartz and found them to be tectonic deformation, not PDFs (Deutsch et al., 1994). Formation of these plannar features was discussed by Leroux and Doukhan (1993). Radar observation without image in (McHone and Greeley, 1997). (Kubik et al., 1998) assumed landslide origin and used material from Koefels to calibrate 10Be and 26Al production rates. (Kubik et al., 1998) refers to (Ivy-Ochs et al., 1998) for the error-weighted mean radiocarbon age 8750±25 years corresponding to the calibrated age (calendar age) of 9800±100 years relative to the year 1995. Erismann and Abele (2001, chap. 2.4) summarized history of investigation at Köfels and the field, theoretical and experimental evidence that shows the Köfels to be a landslide with a frictional melt. Original work documenting the landslide origin of Köfels feature include Erismann (1977), Erismann et al. (1977), Masch et al. (1985), Sørensen and Bauer (2003), and Hermanns et al. (2006). Early structure description by (Suess, 1936). SIR-C radar observation in (McHone and Greeley, 1997). Other referrences to earlier geological studies and C14 dating in (Storzer et al., 1971a)"

Nice. Yes, it's the biggest rockfall crystalline rocks in the alps. The energy was big enough to melt due to the friction of the landslide and produce a special pumice. (Impact melts were the key feature for the meteorite theory.)